Signal-to-noise ratio in pulse reception



Sept. 30, 1952 M. G. NlcHoLsoN, JR 2,612,503

` SIGNAL-TO-OISE RATIO IN PULSE RECEPTION Original Filed July 18, 1945 ATTORNEY atenteci Sept. 30, Q

SICrNAL-'JONOISE RATIO IN vPULSE ,RECEPTION` Maaisono. Nicholson, Jr., Snyder, N. Y., assigner 'to 'Sylvania'Y Electric Products Inc., a corpora-v tion of yMassachusetts vContinuation of application Serial No. 605,691, July 18, 19.45. This application December 15,

1951, 'Serial No.'261,779

titled 'Signal-to-'Noise -Ratio 'in -Pulse Reception,

and assigned 'to "the ksame assignee 'asthe Apresent application.

It 'is 'an object of this invention to provide a method Vand 'apparatus for improving the 'signal- (to-noise ratio in the reception of pulses transmitted at 'a periodic rate.

It is Iaurther object of 'this 4invention to prolvide 'apparatus of the class described in which the voltages corresponding 'to the desired pulses `may 'be'a'dded at one ra'te While voltages of randomnoise `'andstatic are added 'at 'a smaller rate.

It is still a further object of this invention to provide'amethod 'and'a'pparatus 'for adding pulse 'voltages in an 'arithmetical 'manner While adding voltages corresponding to random noise and 'static'in a root-'rnean-squar'e manner.

rvStill'further objectsl and advantages of my invention will be Yapparent "fromthe speci'cation.

The"features 'of novelty which I believe to 'be characteristic of/myinverition are set `forth with particularity in the appended claims. My invention itself, however. both as to its fundamental :principles and 'as to its ,particular embodiments, Willbest'be understood'by reference to the Specification and accompanying drawing, in which: f

Fig. l'is 'a circuit diagram'of one Yform of apparatus in accordance with my invention, and

-Fig. 2 is 'a similar diagram of'a modified form ofapparatusin accordance with my invention.

Referring novvmore particularly to'Fig. 1, 'I0 represents a rod or bar `having l`magnetostrictive properties. This bar'maybe imbedded `at opposite `ends inmasses II and I2, supported on any suitable support I3, vvvhich masses rmay be sufcientiy heavy'an'd rig'id'so as to cause'reiiection ofjmagnetostriction waves "traveling lengthwise in bar I0.

`-Reception of the'desir'ed 'pulses'may be accompli'sh'ed by receiver `and amplifier I4, provided withitheusuahantennaand ground, andthe output pulses maybe supplied to coil I5 surrounding rod I0. Also'surrounding rod I0, but displaced from coil I5, I mayprovide coil I6, the output'of Which'ieeds the -input circuit yof amplifier I'I, and ltheoutput of which vis-impressed onfanyf' suitable indicator, 'suchas oscilloscope I8. Magnets I9 Awill"be1associatedvvith each coil in 2 the usual 'manner for the purpose lof impressing a magnetic field upon 'rod I0.

The operation of my invention may 'now be understood. The pulses received by the yreceiver recur at regular intervals at a predetermined fixed rate. Each pulse sets vup a .magnetostriction wave in rod I0, and this yWave travels in both directions from coil I5, one Wave proceeding toward coil I6 and the other toward mass I I. As the Wave passes through 'coil I6, a voltagewill be set up in this coil which will be amplified in amplifier I'I and indicated on voscilloscope I8. This Wave will continue to travel until'it reaches mass l2, whereupon it will be reflected'back toward coil I6, and onpassngthrough coil 'IS .will again produce a voltage therein which Will be impressed upon the amplifier and indicated by the oscilloscope.

In a similar manner, the Wave traveling from coil I5 'toward mass IIl Vwill reach mass II and will be reflected back to coil I5, and will pass down the rod to coil I6, 'thereby producing 'a voltage therein, will continue von to `mass I2, and will be reflected from there back toward coil I6. Thus itwill'be seen'that'each received pulse sets upa Wave, and vthese Waves travel yback and forth on'rod I0 until their energy is dissipated.

By'choosing'the distance from coil I5 tomass II vso that it is exactly equal to the vdistance of travel of the Vmagnetostriction wave during the time interval between pulses, it will be kseen that the Wave produced by the first pulse received-arrives `Vat mass II just as the second kpulseis being received, and arrives back -atcoil I5 just as the third pulse is being received fand is reinforced by the third pulse.

The distance from coil t5 to mass I2 sis'likewise so related to the time rate of the pulses that each wave reiiected frommass `I2 arrives at coil I5 at the same time that this `coil is impressing, througha received pulse, another wave in the rod. From this time onv the Wave-generated by each incoming pulseis added tothe wave from a preceding pulse which has been reflected `from rone ofthe masses II or I2.

` duce a time delay which may be varied by shifting coil I6, as described Vand claimed in 'my 3 earlier application, Serial No. 541,743, now Patent No. 2,401,094, granted May 28, 1946.

By operating in the manner described, a denite improvement in signal-to-noise ratio can be obtained. The reason for this is that the voltages produced by the various waves when the distances are chosen as above indicated add arithmetically, whereas random noise and static does not add arithmetically, but as root-meansquare. This phenomenon is analogous to the reduction of dust and dirt marks and grain in a motion picture projected at the intended speed as compared with the marks on any individual frame projected as a still picture. The less the attenuation in rod Ill, the greater the improvement'l which can be realized.

Referring now more particularly to Fig. 2, I have shown a modified form of my invention, like reference numbers designating like parts as in Fig. l. 'Ihis figure diiers from Fig. 1 in that,

instead of one output coil, a number may be provided; for instance, I6, 16a, lBb, and more, ir" desired. All of these are preferably connected in series and in the input of amplifier Il, and

the distance between each coil and the next is made such that it is equal to the distance traveled by the wave in rod lil in the time between two successive pulses or any Whole multiple thereof.

In this way, while the wave produced by the iirst pulse is passing through coil |51) and generating a voltage therein, the wave produced by the second pulse is passing through coil 16a and generating a voltage therein, and the wave produced by the third pulse is passing through coil I6 and generating a voltage therein.

The reected action of the waves is the same as described with reference to Fig. l, and the explanation, therefore, is not repeated. In the same manner, as already described, the voltages generated by the desired pulses add arithmetically, whereas the voltages generated by random noise and static add as root-mean-square and, therefore, a substantial improvement in signalto-noise ratio is obtainable.

In the specification I have explained the principles of my invention and the best mode in which I have contemplated applying those principles, so as to distinguish my invention from other inventions; and I have particularly pointed out and distinctly claimed the part, improvement, or combination which I claim as my invention or discovery.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modiiications and changes may be made without departing from the spirit and scope thereof, as will be clear to those skilled in the art.

What I claim is:

1. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated configuration having at least one reiiecting end termination, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from said one end termination by a whole multiple, including one, of one half of said distance for impressing magnetostrictive waves in said member corresponding to each pulse received, and means responsive to impressed and reflected waves in said member for producing output pulse voltages.

2. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated coniiguration having at least one reiiecting end termination, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from said one end termination by a whole multiple, inincluding, of one half of said distance for impressing magnetostrictive waves in said member corresponding to each pulse received, and means spaced from said rst mentioned means by a whole multiple, including one, of said distance for picking up from said member a voltage corresponding to each pulse received.

3. The combination claimed in claim 2, in which said pickup means comprises a plurality of series connected coils longitudinally spaced along said member at points spaced from each other and from said first mentioned means, the distance between any two successive ones of said points being equal to a whole multiple, including one, of said wave-travel distance.

4. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated configuration having reflecting end terminations, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from one of said end terminations by a whole multiple, including one, of one half of said distance for impressing magnetostrictive waves in said member corresponding to each pulse received, means spaced from said first mentioned means by a while multiple, including one, of said distance for picking up from said member a voltage corresponding to each pulse received, the length of said member being selected such that the other of said end terminations is spaced from said second mentioned means by a whole number, including one, of one half of said distance.

5. The combination claimed in claim 4, in which said pickup means comprises a plurality of series connected coils longitudinally spaced along said member with an individual spacing from said first mentioned means and from each other equal to said wave-travel distance.

6. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predeterminedsubstantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated configuration having at least one reflecting end termination, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, a pulse input coil surrounding said member and spaced from said one end termination by a whole multiple, including one, of one half of said distance for impressing magnetostrictive waves in said member corresponding to each pulse received, and a pickup coil surrounding said member and spaced from said input coil a whole multiple, including one, of said distance to have induced in said pickup coil a voltage corresponding to each pulse received.

7. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated conguration, means positioned on each end of said member for causing said member to have reflecting end terminations, a magnetostrictive Wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from one of said end-termination means by a Whole multiple, including one, of one half of said distance for impressing magnetostrictve waves in said member corresponding to each pulse received, means spaced from said rst mentioned means by a Whole multiple, including one, of said distance for picking up from said member a voltage corresponding to each pulse received, the.`

length of said member being selected such that the other of said end-termination means is spaced from said second mentioned means by a whole number, including one, of one half of said distance.

8. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted with a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated conguration having at least one reecting end termination, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from said one end termination by a whole multiple, including one, of said distance for impressing magnetostrictive Waves in said member corresponding to each pulse received, and means spaced from said rst mentioned means by a Whole multiple, including one, of said distance and responsive to impressed and reflected `Waves in said member for producing output pulse voltages.

9. Apparatus for improving the signal-to-noise ratio in the reception of pulses transmitted With a predetermined substantially uniform periodicity comprising, in combination, a magnetostrictive member of elongated configuration having reflecting end terminations, a magnetostrictive wave induced in said member traveling a predetermined distance therein in the time interval between the initiation of successive ones of said pulses, means spaced from one of said end terminations by a whole multiple, including one, of said distance for impressing magnetostrictive waves in said member corresponding to each pulse received, means spaced from said first mentioned means by a Whole multiple, including one, of said distance and responsive to impressed and reflected waves in said member for producing output pulse voltages, the length of said member being selected such that the other of said end terminations is spaced from said second mentioned means by a Whole multiple, including one, of said distance.

MADISON G, NICHOLSON, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,561,278 Pupin Nov, 10, 1925 2,318,417 Phelps May 4, 1943 2,401,094 Nicholson, Jr. May 28, 1946 2,401,416 Eaton et al. June 4, 1946 2,495,740 Labin et al Jan. 31, 1950 FOREIGN PATENTS Number Country Date 490,864 Germany Feb. 8, 1930 

